powering a hydraulic chainsaw off your tractor's hydraulic system

[dfkrug]

....or..."Hydraulic Chainsaws for Fun and Profit"

A long time ago, I fantasized about building a boom-mounted chainsaw to connect
to my loader. This would allow me to trim branches off trees from the seat of
my tractor. The loader can already reach more than 8 feet high, and the
boom I pictured would add maybe another 8-10 feet.

Kinda like this:
LIMBHOG Details
or this:
LimbSaws by Priefert | Home

I imagined powering the unit with 12V DC or hydraulic power, both available
from the tractor. I have always viewed tractors as a mobile hydraulic "power-pack".
Why not use it?

12DC has its limitations, for sure, even tho you can buy 12V DC hand-held chainsaws.
I run the hydraulics on my FEL-mounted manlift off the tractor's battery, but I cheat, and
use a DC/hydraulic power-pack. Not ideal, either, but it was already set up that way.

Well, I have a friend who is really really into chainsaws, and I suggested he might want
to try a hydraulic pole saw, run off the tractor, so he could trim branches without getting
off the tractor. It would be hand-held and stored on hooks connected to his ROPS when not
in use. Similar to what the pro tree trimmers use when operating snorkle trucks. If he
acquired one, I would figure out and set up the hydraulics for him.

I was suggesting using a modified older cheaper unit like this:

 

[dfkrug]

Well, "this" is a Stanley saw, built shortly after they acquired Ackley Hydraulics, a
pioneer in hyd saws. Purchased on eBay for under $200, I quickly discovered
that it used closed center hydraulics, and specs limited it to 2000 psi. 5GPM flow
was just about right.

Apparently early hydraulic power supplies for hyd saws were closed center, while
later ones were open center. Newer saws came with a control valve that let you
opt for either one. I suspect that newer bucket trucks owned by utilty companies
use OC, and manufacturers want to stay compatible with older CC power supplies.

After cleaning it up and adapting to JIC fittings, I tested the saw using my tractor's
AUX circuit. It worked fine, but releasing the trigger control forces the implement
pump to send all flow thru the tractor relief valve. These saws do not have their own
RV, so I was very careful not to bog the saw down. My tractor puts out 2500psi.

You can perform this kind of wet test (briefly!) on CC hyd devices if you are careful.

 

[J_J]

When you decide on a hyd chainsaw, notice whehter it is open center or closed center or switchable.

The relief valve is around 1500 psi.

I have one of those chainsaws pictured, but it is closed centered, and my system is open center. I will have to figure out how to run it off the open center system. I am thinking I can lock the trigger down, and have the flow controlled by an open center valve.

I also have a hyd back pack with a chainsaw pole mounted saw that tree surgeons use in their bucket trucks. Some of the units also have a hyd powered circular blade for the trimming.

You can probably make a hyd powered saw unit out of a small hyd motor, sprocket and chain to match.

You would want a motor spool for the control valve.

You can also make something like I put together years ago.

 

[dfkrug]

Next up were these two modern saws, both unused, and also purchased off of eBay:

First is a Reliable polesaw, commonly used by utility companies everywhere.

Both of these saws run way north of $1000 new, but you can get them for $500-600
in this condition, if you are patient. Our utility prob pays over $2000 for the Reliable;
they can just pass the cost on to ratepayers.

 

[dfkrug]

Next up is probably the most common hydraulic saw out there, a Fairmont, which is now
part of Greenlee. Similar cost to the Reliable, new or used. Acquired on eBay.

This saw, like the Reliable above, is limited by the manufacturer to 2000psi, but has no
relief valve. All 3 saws run at an optimum flow of 5GPM.

I should also mention that both of the newer saws have a small valve to allow a certain
amount of hyd oil leakage to lubricate the bar/chain. It works quite well.

 

[dfkrug]

Here is the valve you turn to go from OC to CC. OC is the factory setting, implying most
power sources are open center.

Note that the trigger valves on all 3 saws are not "motor-spool" valves; flow to both sides
of the motor is shut off when the valves are released. Since there is no significant momentum
in the chain moving at full speed, a motor-spool is not necessary (OC). Top speed for the chains,
BTW, is considerably slower than on a gas chainsaw. You can also start the cut with the chain
stopped, but already pushed into the wood. Enormous torque is available as soon as you
pull the trigger.

This also means that there is no need for a chain brake. The chain stops very quickly.

 

[dfkrug]

Finally, I had the hydraulics to deal with.

Most modern deluxe CUTs now use implement pumps that run about 2500psi and a max
flow of about 8-9GPM. Smaller, older, or "standard" CUTs are often set at only 1700-2100psi.

If you have the latter, and want to run these saws off your tractor, you are almost there.
Just get a couple of hoses/fittings and connect to your AUX in/out connections. You may
have to hold the AUX valve open if you don't have detented valves. You do NOT want to
run the flow backwards, either.

For the rest of us, a "crossover relief valve" is required. I am not going to risk running
2500psi thru an unprotected 2000psi hyd motor. So, I ordered this one from HydraForce, about
$65, after all the disti markups. This valve is preset at 2000psi, and is small and light.

For both saws, I used this RV, and about 15 total feet of 3/8" hose. 3/8" is the smallest
hose you would want with this kind of flow and hose length.

 

[TomSeller]

It looks like the limbsaw/limbhog has built in break-away in case the saw hangs up as the branch falls? they sure are $$$$

 

[dfkrug]

Running these saws.

Both of the modern saws run extremely well, and no hearing protection is needed. You
CAN stall them, however. My test logs were 12" dry oak, a difficult cut for any saw, but
perhaps those gas saws of more than 50cc.

I found the pole saw to be lighter and easier to use versus the top-of-the-line Stihl polesaw,
due to weight and balance. As for the Fairmont saw, it works great, but it is not big enough
for large logs and the hoses are a hassle. I will continue to use the 5 or 6 gas saws I have,
of different sizes for different duties.

Now back to the original fantasy. I think that the old Stanley would work fine as boom saw
mounted to the FEL. The trigger valve would be modified to be always open, and the control
valve would be the AUX valve down near the driver's seat. Just flick the lever whenever you
are ready to cut. I will prob put the Stanley back on eBay, however. The Fairmont is also mine,
but I may not keep it, and it seems wasteful to modify such a valuable saw when cheaper
alternatives are avaliable.

 

[dfkrug]

It looks like the limbsaw/limbhog has built in break-away in case the saw hangs up as
the branch falls?

They must have some sort of hinge on the boom so that they do not put too much weight
on the chain and bar. I would make a pivot as close to the end as possible.